Fix _upperCaseLetter always returning capital dotted I for locale az_.

PiperOrigin-RevId: 383854930
diff --git a/analysis_options.yaml b/analysis_options.yaml
index d18178b..4cce960 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -1,4 +1,7 @@
 analyzer:
+  enable-experiment:
+  - non-nullable
+
   language:
     strict-raw-types: true
 
diff --git a/lib/intl.dart b/lib/intl.dart
index 2aab2b9..e03b0e5 100644
--- a/lib/intl.dart
+++ b/lib/intl.dart
@@ -559,7 +559,7 @@
 String _upperCaseLetter(String input, String? locale) {
   // Hard-code the important edge case of i->İ
   if (locale != null) {
-    if (input == 'i' && locale.startsWith('tr') || locale.startsWith('az')) {
+    if (input == 'i' && (locale.startsWith('tr') || locale.startsWith('az'))) {
       return '\u0130';
     }
   }